The present invention relates to a thermal diffusion sheet for diffusing heat generated by a heat emitting body, such as an electronic part.
In recent years, the amount of power consumed in electronic parts, for example, central processing units (CPUs) and integrated circuits (ICs), and the amount of heat emitted from these parts have been increasing along with the performance of computers. The processing performance of electronic parts decreases due to heat, and therefore, it is necessary to prevent the temperature from rising due to the heat from the electronic parts. In this connection, a configuration is known in which a thermal diffusion sheet, for example, a graphite sheet, is placed between electronic parts and a housing. Graphite sheets have anisotropic thermal conductivity in such a manner that the thermal conductivity in the direction parallel to the surfaces, that is to say, in the direction of the plane, is much higher than that in the direction of the thickness. Therefore, when a graphite sheet is placed between the electronic parts and the housing, the heat generated by the electronic parts is radiated while being diffused, and thus, the performance of the electronic parts is prevented from decreasing due to a rise in the temperature.
Japanese Laid-Open Patent Publication No. 11-087959, for example, discloses a heat radiating apparatus that is provided with a collector, which is heat collecting means, a flexible heat conducting device, which is led out from the collector, and a heat pipe, which is heat transferring means. In the case of this heat radiating apparatus, the flexible heat conducting device is formed by layering a plastic sheet on top of a graphite sheet. Japanese Laid-Open Patent Publication No. 2000-081143 discloses a packing material made up of a multilayer body in which graphite films and plastic films are alternately layered on top of each other. Japanese Laid-Open Patent Publication No. 2002-012485 discloses a method for coating the two sides of a graphite sheet with an epoxy resin.
Incidentally, thermal diffusion sheets as described above are pasted to electronic parts, such as CPUs and ICs, through manual operations or by a machine in the manufacturing process for electronic devices and the like. These electronic parts are very small, and therefore, it is very difficult to accurately paste a thermal diffusion sheet in a predetermined location. In addition, heat generated by the electronic parts cannot be efficiently radiated when the thermal diffusion sheet is not accurately pasted in the right location, and there is a risk that the performance of the electronic parts may decrease due to a rise in the temperature. For these reasons, a thermal diffusion sheet which can be easily and precisely positioned relative to a heat emitting body, such as an electronic part, is in strong demand.